Insulated rim board and building structure employing same

ABSTRACT

A three-piece insulated rim board for use in a building structure comprises first and second elongate structural layers and an intermediate elongate insulating layer sandwiched between and bonded to the first and second structural layers.

FIELD OF THE INVENTION

The present invention relates generally to building structures and in particular, to an insulated rim board and building structure employing the same.

BACKGROUND OF THE INVENTION

In flooring systems, rim boards run around the perimeter of the building structure and serve as framing members to enclose the floor joists. Typically the rim boards sit on sill plates that rest on the building structure foundation. Floor sheathing that spans the floor joists overlies the rim boards to provide a generally planar support surface for the load bearing exterior walls of the building structure.

Elongate lengths of oriented strandboard (OSB) are commonly used as rim boards. Although OSB rim board has been widely accepted, the thermal rating of OSB rim board is less than desired. To address this problem, insulated rim boards have been considered such as those supplied by Emercor Ltd. of Calgary, Alberta. The Emercor insulated rim board comprises a polyurethane foam core sandwiched between a pair of OSB skins. Lengths of 2″ by 2″ lumber run along the top and bottom surfaces of the foam core between the OSB skins. Although this rim board has better thermal characteristics than conventional OSB rim board, problems exist in that the design of the insulated rim board does not permit the width (i.e. vertical dimension) of the rim board to be altered at the building site due to the fact that altering the width of the insulated rim board changes its load bearing characteristics. As a result, to employ effectively the Emercor insulated rim board at a construction site, a stockpile of different size rim boards must be maintained.

As will be appreciated, rim boards that have good thermal characteristics and permit on-site width adjustment are desired. It is therefore an object of the present invention at least to provide a novel insulated rim board and building structure employing the same.

SUMMARY OF THE INVENTION

Accordingly, in one aspect there is provided a three-piece insulated rim board comprising:

first and second elongate structural layers; and

an intermediate elongate insulating layer sandwiched between and bonded to said first and second structural layers.

In one form, the intermediate layer is formed of foam material such as for example expanded polystyrene foam, urethane foam, polyurethane foam and isocyanurate foam. The intermediate layer has thickness in the range of from about 2½″ to about 7⅜″. The rim board is symmetrical about vertical and horizontal planes coincident with the central longitudinal axis of the rim board. Each of the first and second structural layers has a thickness in the range from about ⅛″ to about 1⅛″. The first and second structural layers are formed of material selected from plywood, oriented strandboard (OSB), metal sheet or other suitable material.

According to another aspect there is provided a floor structure for a building structure comprising:

insulated rim boards running around the perimeter of said building structure and sitting on sill plates; and

joists framed by said rim boards, wherein said insulated rim boards are alterable in vertical dimension without changing the symmetry of the rim boards above the sill plates when looking at the rim boards in side elevation.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described more fully with reference to the accompanying drawings in which:

FIG. 1 is a perspective view, partly cut-away, of a floor structure employing an insulated rim board;

FIG. 2 is a side cross-sectional view of the floor structure of FIG. 1;

FIGS. 3 a and 3 b show tie and angle plates used in the floor structure of FIG. 1; and

FIG. 4 is a side cross-sectional view of an alternative floor structure employing an insulated rim board.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Turning now to FIGS. 1 to 3 b, a portion of a floor structure within a building structure is shown and is generally identified by reference numeral 20. The floor structure 20 comprises insulated rim boards 22 that run around the perimeter of the building structure. The rim boards 22 sit on sill plates 24 that rest on the building structure foundation 26. Tie plates 28 that span the exterior interface between the sill plates 24 and the rim boards 22 are secured to the sill plates 24 and rim boards 22 using suitable fasteners 30, such as for example nails or screws, at spaced locations about the perimeter of the building structure. The rim boards 22 serve as framing members to enclose I-joists 32. Floor sheathing 34 spans the I-joists 32 and overlies the rim boards 22 to provide a generally planar support surface for the external walls 36 of the building structure. Fasteners 38, such as for example nails or screws, secure the external walls 36 to the I-joists 32 and floor sheathing 34. The floor sheathing 34 is toe-nailed to the rim boards 22 and the I-joists 32 by suitable fasteners 39, such as for example nails or screws and is secured directly to the I-joists 32 by suitable fasteners (not shown), such as for example nails or screws.

The I-joists 32 are toe-nailed to the sill plates 24 using suitable fasteners 40, such as for example nails or screws. Angle plates 42 are also secured to the upper surface of the sill plates 24 and the interior surface of the rim boards 22 using suitable fasteners 44, such as for example nails or screws, at spaced locations about the building structure.

Each insulated rim board 22 is of a three-piece structure and comprises an intermediate insulating layer or core 60 sandwiched between and bonded to interior and exterior structural layers or panels 62 and 64 respectively by suitable adhesive such as for example urethane adhesive. In this embodiment, the intermediate insulating layer 60 is formed of expanded polystyrene (EPS) foam and has a thickness equal generally in the range of from about 2½″ to about 7⅜″. The thickness of the intermediate insulating layer 60 is selected to give the rim board 22 the desired thermal rating. The interior and exterior structural layers 62 and 64 are formed of a suitable structural material such as for example oriented strandboard (OSB) or plywood and have a thickness generally in the range of from about ⅛″ to about 1⅛″. The thickness of the interior and exterior structural layers 62 and 64 is typically selected to give the rim board 22 the desired fire rating. In this embodiment, the rim board 22 when viewed in side elevation is symmetrical about a horizontal plane coincident with the central longitudinal axis of the rim board 22. The rim board 22 is also symmetrical about a vertical plane coincident with the central longitudinal axis of the rim board.

Typically, the rim boards 22 are manufactured in standard widths W (e.g. 9½″, 11⅞″, 14″ and 16″) to match conventional I-joist sizes. Notwithstanding, due to the symmetrical design of the rim boards 22, the widths of the rim boards 22 can be altered (i.e. reduced) on-site when needed to accommodate for example steps, windows etc. without compromising the load bearing characteristics or thermal characteristics of the rim boards 22. As a result, rim boards 22 of any standard width can be tailored on-site to satisfy construction needs.

FIG. 4 shows a floor structure employing an alternative rim board 122. The rim board 122 is very similar to that described in the previous embodiment and comprises interior and exterior structural layers or panels 162 and 164 sandwiching an intermediate insulating foam layer 160. Unlike the previous embodiment however, the exterior structural layer 164 in this embodiment has an increased vertical dimension W as compared to the interior structural layer 162 and intermediate foam layer 160 and extends to the building foundation 26. As a result, the sill plates 24 abut the exterior structural layers 164 and only support the interior structural layers 162 and intermediate foam layers of the rim boards 122. The exterior structural layers 164 are supported by the building structure foundation 26. Although the overall symmetry of the rim board 122 is lost by extending the dimension of the exterior structural layer 164, above the sill plates 24, the rim board is symmetrical allowing the rim board 122 to be altered on-site as discussed above to suit construction needs.

Although dimensions for the rim boards are provided above, those of skill in the art will appreciate that the dimensional information is exemplary. Depending on the environment in which the rim boards are being deployed, the overall dimensions of the rim boards may vary from those discussed above.

In the embodiments described above, the interior and exterior structural layers are described as being formed of OSB or plywood. Those of skill in the art will appreciate that the interior and exterior structural layers may be formed of other suitable structural material such as for example metal sheet, fire resistant board etc. Also, the intermediate foam layers need not be formed of EPS. Other foam material such as for example urethane foam, polyurethane foam, isocyanurate foam etc. or other suitable non-foam material such as for example honeycomb board may be used.

Although embodiments have been described above with reference to the drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims. 

1. A three-piece insulated rim board comprising: first and second elongate structural layers; and an intermediate elongate insulating layer sandwiched between and bonded to said first and second structural layers.
 2. An insulated rim board according to claim 1 wherein said intermediate layer is formed of foam material.
 3. An insulated rim board according to claim 2 wherein said foam material is one of expanded polystyrene foam, urethane foam, polyurethane foam and isocyanurate foam.
 4. An insulated rim board according to claim 2 wherein said intermediate layer has a thickness in the range of from about 2½″ to about 7⅜″.
 5. An insulated rim board according to claim 3 wherein said intermediate layer has a thickness in the range of from about 2½″ to about 7⅜″.
 6. An insulated rim board according to claim 1 wherein the rim board is symmetrical about vertical and horizontal planes coincident with the central longitudinal axis of the rim board.
 7. An insulated rim board according to claim 2 wherein the rim board is symmetrical about vertical and horizontal planes coincident with the central longitudinal axis of the rim board.
 8. An insulated rim board according to claim 7 wherein said foam material is one of expanded polystyrene foam, urethane foam, polyurethane foam and isocyanurate foam.
 9. An insulated rim board according to claim 7 wherein said intermediate layer has a thickness in the range of from about 2½″ to about 7⅜″.
 10. An insulated rim board according to claim 1 wherein said first and second structural layers are formed of material selected from plywood, oriented strandboard (OSB), metal sheet or other suitable material.
 11. An insulated rim board according to claim 10 wherein each of said first and second structural layers has a thickness in the range of from about 1/8″ to about 1⅛″.
 12. An insulated rim board according to claim 2 wherein said first and second structural layers are formed of material selected from plywood, oriented strandboard (OSB), metal sheet or other suitable material.
 13. An insulated rim board according to claim 12 wherein each of said first and second structural layers has a thickness in the range of from about 1/8″ to about 1⅛″.
 14. An insulated rim board according to claim 7 wherein said first and second structural layers are formed of material selected from plywood, oriented strandboard (OSB), metal sheet or other suitable material.
 15. An insulated rim board according to claim 14 wherein each of said first and second structural layers has a thickness in the range of from about ⅛″ to about 1⅛″.
 16. A floor structure for a building structure comprising: insulated rim boards running around the perimeter of said building structure and sitting on sill plates; and joists framed by said rim boards, wherein said insulated rim boards are alterable in vertical dimension without changing the symmetry of the rim boards above the sill plates when looking at the rim boards in side elevation.
 17. A floor structure according to claim 16 wherein each rim board is of a three-piece construction comprising first and second elongate structural layers and an intermediate elongate insulating layer sandwiched between and bonded to said first and second structural layers.
 18. A floor structure according to claim 17 wherein the intermediate layer of each rim board is formed of foam material.
 19. A floor structure according to claim 18 wherein said foam material is one of expanded polystyrene foam, urethane foam, polyurethane foam and isocyanurate foam.
 20. A floor structure according to claim 19 wherein the intermediate layer of each rim board has a thickness in the range of from about 2½″ to about 7⅜″.
 21. A floor structure according to claim 17 wherein each rim board is symmetrical about vertical and horizontal planes coincident with the central longitudinal axis of the rim board.
 22. A floor structure according to claim 17 wherein the first and second structural layers of each rim board are formed of material selected from plywood, oriented strandboard (OSB), metal sheet or other suitable material.
 23. A floor structure according to claim 22 wherein the first and second structural layers of each rim board have thicknesses in the range of from about ⅛″ to about 1⅛″. 